Communication systems allow information to be transmitted from one location to another via a communication medium. The communication medium may be bounded, such as a wireline medium, or unbounded, such as a wireless medium. The communication system can include (1) a transmitter that modulates information onto carrier wave(s) and transmits it on the communication medium and (2) a receiver that receives the carrier wave(s) and demodulates the signal to obtain the information. Various signal processing systems have been used to modulate information onto the carrier wave(s) and demodulate the carrier wave(s) to obtain the information.
An example of one such system is a spread spectrum communication system. Transmitted signals in spread spectrum communication systems are spread over bandwidths larger than the bandwidths needed to transmit the information to promote privacy of the information. A spread spectrum system may utilize one or more techniques to transmit information. Examples of such techniques include frequency-hopping spread spectrum, direct-sequence spread spectrum, time-hopping spread spectrum, and chirp spread spectrum.
In a direct-sequence spread spectrum (DSSS) system, the bandwidth of a transmitted signal is increased by modulating the signal onto a known pseudo-noise (PN) coded signal before modulating onto the carrier wave(s). Typically, the coded signal is a digital signal having approximately an equal number of high and low bits that maximizes the spectrum over which the signal is spread. A DSSS receiver may recover the transmitted information by demodulating the carrier wave(s) and then multiplying the resulting signal with a local replica of the PN coded signal to eliminate the PN coded signal. The DSSS technique spreads energy over a wider bandwidth and promotes information privacy since a receiver must know the PN coded sequence used in the transmission to recover transmitted information efficiently.
A spread spectrum receiver in some communication systems may be required to receive different DSSS signals. When two or more packets of information overlap each other, the receiver may be unable to process both packets of information. Accordingly, spread spectrum receivers are desirable that can receive and process two or more different signals that at least partially overlap in time and in frequency.